Differential Diagnoses for Respiratory Symptoms

Clinical Presentation and Diagnosis

The American College of Chest Physicians recognizes that low-grade fever with productive cough and bilateral rhonchi are classic features of acute bronchitis 2
Viruses including coronavirus, rhinovirus, and adenovirus cause acute bronchitis with predominant symptoms of nasal congestion, rhinorrhea, and pharyngitis 1
Approximately 40% of previously healthy individuals develop transient airflow obstruction and bronchial hyperresponsiveness after acute viral respiratory infections, which explains the scattered rhonchi 1
The college campus setting increases risk for viral outbreaks, with up to 36% showing mixed viral infections in these environments 3
The American College of Chest Physicians emphasizes that chest radiograph is essential to differentiate pneumonia from acute bronchitis, as physical examination alone cannot reliably exclude pneumonia 4
The absence of focal consolidation, egophony, or fremitus on physical exam reduces but does not eliminate pneumonia probability 4
Chest radiograph is mandatory to rule out infiltrates before concluding this is uncomplicated bronchitis 4
The presence of fever lasting more than 4 days would increase suspicion for bacterial pneumonia 2
Do not assume clear/whitish sputum indicates viral infection or that purulent sputum indicates bacterial infection—sputum color alone does not reliably predict bacterial etiology 4

Mycoplasma pneumoniae and Chlamydophila pneumoniae are causally linked to acute bronchitis in otherwise healthy individuals, particularly in college campus outbreaks 1, 3
Patients with documented M. pneumoniae or C. pneumoniae infections have significantly lower FEV1 values and greater degree of reversibility than those with viral etiologies 1
Prospective surveys show M. pneumoniae and C. pneumoniae are rare causes (<1%) in unselected patients with 5-day cough, but incidence increases substantially in outbreak settings 1, 3

The American College of Chest Physicians recommends routine antibiotics are NOT indicated for immunocompetent adults with acute bronchitis, even when atypical pathogens are suspected, unless the condition worsens 4
Antibiotics should only be considered if symptoms persist beyond 48-72 hours or clinical deterioration occurs suggesting bacterial superinfection 4, 2
Do not miss pneumonia by failing to obtain chest radiograph when fever and productive cough are present with systemic symptoms 4
Do not prescribe antibiotics empirically for presumed acute bronchitis in an immunocompetent patient without evidence of bacterial pneumonia or pertussis 4
Reassess within 48-72 hours if symptoms worsen or fail to improve, as this may indicate bacterial superinfection or alternative diagnosis 4, 2